Association of Atoms into Universal Dimers Using an Oscillating Magnetic Field

Abstract

In a system of ultracold atoms near a Feshbach resonance, pairs of atoms can be associated into universal dimers by an oscillating magnetic field with frequency near that determined by the dimer binding energy. We present a simple expression for the transition rate that takes into account many-body effects through a transition matrix element of the contact. In a thermal gas, the width of the peak in the transition rate as a function of the frequency is determined by the temperature. In a dilute Bose-Einstein condensate of atoms, the width is determined by the inelastic scattering rates of a dimer with zero-energy atoms. Near an atom-dimer resonance, there is a dramatic increase in the width from inelastic atom-dimer scattering and from atom-atom-dimer recombination. The recombination contribution provides a signature for universal tetramers that are Efimov states consisting of two atoms and a dimer.

Two- and three-body problem with Floquet-driven zero-range interactions

“…Modulation frequencies were reported as high as 1 MHz [37]. Recently a theory was published which explains magneto-association in the case of an oscillating magnetic field [38]. This extended a previous work [39] to include many-body effects in a perturbative treatment involving Tan's contact [40].…”

“…When R |a| (or for all R when a = ∞) we can neglect the last term in the right hand side of Eq. (38) and arrive at the well-known inverse-square scaling ω(R) = −C 2 /R 2 , where C ≈ 0.567 is the solution of exp(−C) = C. We expect this scaling to occur in the driven problem when we are exactly on the Floquet resonance (a eff = ∞), at least, for sufficiently large R where we can neglect the interference effects of the closed-channel evanescent waves (with n < 0) and consider the light-heavy interaction as if it is undriven and characterized by an infinite scattering length. Indeed, this is what we observe in Fig.…”

Hydrodynamics with spacetime-dependent scattering length

“…In addition, an interparticle interaction is not only tunable in its magnitude and sign with the magnetic field via Feshbach resonances [6], but also variable over space and time at will to a reasonable extent [7][8][9]. While such a spacetime-dependent scattering length has been proposed to realize a number of intrigu-ing phenomena [10][11][12][13][14][15][16][17][18][19][20], it may also be useful as a novel probe of target systems.…”

Effective Atom–Molecule Conversions Using Radio Frequency Fields

“…[12] PA can be also viewed as acontinuum-to-bound transfer process, but it seems to be incoherent unless the atomics ystem is ac oherent many-body state such as in aq uantum degenerate gas. [13][14][15] In the same vein, ar adio frequency (RF)f ield or an oscillating magnetic field can also be au seful tool to associate cold atoms into molecules, [16][17][18] with the advantage that it avoids spontaneous emission decay processes since it couplesa toms in the ground electronic states. The use of RF fields as ab inding mechanism in an ultracold atomic ensembles eems to offer encouraging opportunities for observing coherent population transfer betweenc ontinuum and bound states.…”